Oscillation generator



Dec. 16, 1930. w, MARRlSON 1,785,036

OSCILLATION GENERATOR Filed Dec. 30. 1927 Patented Dec. 16, 1930 UNITEDSTATES PATENT OFFICE WARREN A. MARRISON, OF ORANGE, NEW JERSEY, ASSIGNORT0 BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N. Y., ACORPORATION OF NEW YORK OSCILLATION GENERATOR Application filed December30, 1927.

This invention relates to oscillators or generators employing mechanicalvibratory systems, and more particularly to those including apiezo-electric crystal adapted to determine the frequency of theoscillations generated.

An object of the invention is to prevent variations in temperaturefrom'causing variations in the rate of vibration of such a system.

As is well known, the rate of vibration of a piezoelectric crystal, suchas a quartz crystal, is dependent to some extent on its temperature. Inorder to maintain the vibrations at a frequency constant irrespective oftemperature variations, it is necessary to provide means forcompensating such varia tions.

It is also well known that the rate of vibration of a piezoelectriccrystal is dependent to some extent upon the separation between thecrystal and the electrodes associated with it. Thus, if one electrode isbrought closer to the crystal a slight decrease in its rate of vibrationoccurs, and, vice versa, a slight increase in its rate of Vibrationoccurs when the electrode is moved farther from the crystal.

In a specific embodiment, the object of this invention is accomplishedby mounting on a fixed support or supports one or both electrodes, eachconsisting of two elements having different coefficients of expansion.Obviously, separate electrodes may be used and one or both may becarried by supporting members consisting of two elements havingdifferent coefficients of expansion, secured to the fixed supports. Whena change in temperature occurs, which tends to cause a change in therate of vibration of the crystal, the position of the electrode orelectrodes with respect to the crystal will be changed to introduce acompensating effect adapted to maintain the crystal oscillating at aconstant frequency.

In the drawings, Fig. l is a plan view, partly broken away, of oneembodiment of the invention;

- Fig. 2 is a side elevation, partly in sectlon, taken along line 22 ofFig. 1; and

Serial No. 243,604.

Fig. 3 is a side elevation, partly in section, of another embodiment.

I11 Figs. 1 and 2 there is shown a container 6 for enclosing apiezo-electric cr stal 3. The container is provided with a li or cover1, secured in position by screws or bolts 2.

Mounted within the container 6 on cap screws 7, having heads 8, are twoelectrodes 4:, 5, which are spaced from the cover, and relatively toeach other, by sleeves 9. The cap screws are secured to the cover bymeans of nuts 10, and are surmounted by binding posts 11.

The electrodes l and 5 are each made of two metals having differentcoeliicients of expansion. When the temperature changes the electrodeswill expand unequally, and their positions with respect to the crystalwill be changed.

The frequency at which the crystal oscillates depends upon temperatureand also upon the separation between the crystal and its electrodes. Byproperly selecting and dimensioning the elements of which theseelectrodes are composed, any change in the frequency of the crystal, dueto temperature variations, may be compensated by an equal but oppositechange due to variation of the position of the electrodes with respectto the crystal.

The physical dimensions of the crystal. also vary with changes intemperature. lVhile this factor is so small as to be negligible for thepurpose of this invention, it may be taken into account and theelectrodes may be designed to compensate for it.

Another embodiment of the invention is illustrated in Fig. 3. Acontainer 6 has a cover 1 secured thereto by bolts 01 screws 2. Mountedwithin the container 6 on bimetallic elements 12 attached to cap screws7, having heads 8, are two electrodes 4, 5, of which electrode 5 isspaced from the cover and relatively to the other electrode by a sleeve9. A piezo-electric crystal 8 may be mounted on electrode 5. The capscrews are attached to the cover by nuts 10, and are sur mounted bybinding posts 11.

The operation of the device of Fig. 3 is substantially similar to thatdescribed above.

The bi-metallic members 12 are so Selected and dimensioned that a changein temperature causes the position of the electrodes l and 5 to bevaried to compensate the change in the resonant frequency of the crystaldue to temperature variations, whereby the frequency at which thecrystal oscillates remains constant despite Variations in temperature.

What is claimed is:

1. In combination an oscillator, and means for mounting said oscillatorfor connection in an electrical circuit, said means comprising anelectrode composed oi metals having different coeliicients of expansion.

2. A holder for piczo electric resonator comprising a mounting member,two bolts secured thereto, an electrode secured to each said bol, saidelectrodes each consisting of lei-metallic elements.

3. A holder for a piezo electric resonator comprising a container, acover therefor, a

plurality of bolts extending inwardly of said cover and a lei-metallicelectrode secured to each said bolt.

4. A holder for a piczo electric resonator comprising a container, acover therefor, a plurality of mounting elements secured to said cover,and a bi-metallic element secured a; to each said element.

In witness whereof, I hereunto subscribe my name this 29th day ofDecember, 1927.

VAR-BEN A. MARRISON.

